1. Field of the Invention
The present invention relates to gamut mapping of colors in a color image, and in particular relates to selection of different gamut mappings for different regions of an image based on a spatial frequency analysis of the image.
2. Description of the Related Art
Gamut mapping is a well-known procedure by which colors in a color image that are not reproducible by an output device are mapped to reproducible colors, while preserving the perception of good color fidelity and colorfulness.
Many different gamut mapping algorithms have been proposed, and it is known that some types of color images are gamut-mapped better with some gamut mapping algorithms than others. For example, it is known that computer graphic images having only a few highly saturated colors, such as might be found in a presentation, are gamut mapped more accurately by preserving saturation rather than by preserving hue. On the other hand, for natural scene photographic images, better gamut-mapped results are obtained by preserving hue and hue gradation. It has therefore been considered to analyze an image as a whole, or analyze each region in an image, so as to identify images or regions thereof for which different gamut mapping algorithms should be applied based on content.
It has heretofore been difficult, however, to identify content of an image or regions thereof, so as to select an appropriate gamut mapping algorithm. In particular, classification of objects in an image, or classification of the image itself, often depends on artificial and/or empirical rules which through trial and error have been found to work on some images, but which do not work on all.